Coronary heart disease remains the leading cause of cardiovascular morbidity and mortality. The relationship between perioperative blood glucose variability (BGV), microcirculatory changes, and subsequent organ dysfunction after coronary artery bypass grafting (CABG) remains poorly defined. Associations among BGV, sublingual microcirculation, and organ dysfunction, as measured by the Cardiac Surgery Score (CASUS) were evaluated.

Prospective cohort study.

A tertiary academic cardiac hospital and a secondary cardiac hospital.

51 adult patients undergoing elective on-pump CABG.

None.

Perioperative BGV was quantified using standard deviation (SD), coefficient of variation (CV), and mean amplitude of glycemic excursions. Sublingual microcirculation, including the proportion of perfused vessels (PPV) and perfused vessel density, was assessed. The primary outcome was organ dysfunction on postoperative day 1, defined by a CASUS >6.5. Higher perioperative BGV correlated significantly with impaired microcirculation and metabolic stress. CV was negatively associated with PPV (r = –0.309, p < 0.05) and positively with lactate (r = 0.280, p < 0.05). Postoperative BGV metrics were significant indicators of organ dysfunction, demonstrating high discrimination for SD (area under the curve [AUC] 0.952), CV (AUC 0.931), and mean amplitude of glycemic excursions (AUC 0.936). An optimal SD cutoff of 56.98 mg/dL identified at-risk patients with 100% sensitivity and 91.5% specificity. Furthermore, impaired admission microcirculation was strongly associated with subsequent organ failure. Lower admission PPV (AUC 0.963) and perfused vessel density (AUC 0.918) were significantly associated with high CASUS scores on postoperative day 1.

Postoperative BGV and early microcirculatory impairment are associated with high risk for organ dysfunction in CABG patients. Integrating BGV control with bedside microcirculatory and lactate monitoring may strengthen early risk stratification and management.